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Old 10-24-2011, 12:54 AM   #1
smata67
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Default 90 minute mash?

I'll be doing the BMW Dubbel Trouble:

http://www.brewmasterswarehouse.com/...double-trouble

Do I have to mash for the full 90 minutes, or can I do the iodine test at 60 and be good? Are there any benefits to mashing beyond conversion?


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Old 10-24-2011, 01:00 AM   #2
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It's about more than just conversion. That's got a lot of pilsner malt. The extra 30 minutes are needed to drive off SMM (S-Methyl methionine) which is a DMS precursor and commonly found in low kilned malts like pilsner.


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Old 10-24-2011, 01:27 AM   #3
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It's about more than just conversion. That's got a lot of pilsner malt. The extra 30 minutes are needed to drive off SMM (S-Methyl methionine) which is a DMS precursor and commonly found in low kilned malts like pilsner.
He said mash, not boil, btw.
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Old 10-24-2011, 01:32 AM   #4
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Originally Posted by smata67 View Post
I'll be doing the BMW Dubbel Trouble:

http://www.brewmasterswarehouse.com/...double-trouble

Do I have to mash for the full 90 minutes, or can I do the iodine test at 60 and be good? Are there any benefits to mashing beyond conversion?
If you're mashing closer to ~149 it might take longer than 60 minutes. I'd say, however, that if an iodine test says you're converted you should be fine.
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Old 10-24-2011, 01:49 AM   #5
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He said mash, not boil, btw.
you're right, my bad. Read mash, thought boil.
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Old 10-24-2011, 01:50 AM   #6
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you're right, my bad. Read mash, thought boil.
No worries.
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Old 10-24-2011, 02:29 AM   #7
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If you're mashing closer to ~149 it might take longer than 60 minutes. I'd say, however, that if an iodine test says you're converted you should be fine.
Iodine test is minimum criteria, but not adequate. Iodine test will come back negative long before conversion to maltose is completed. It only tests for large starches. Once alpha has broken down into medium chains iodine test will be negative, but its still highly unfermentable.

A low beta dominant (below 147ish), or a low diastatic mash (mostly amber/brown malt) might take 90 minutes...but, a 150+, mostly pale malt mash is done well before the 60 minute mark, let alone 90.
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Old 10-24-2011, 02:34 AM   #8
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Iodine test is minimum criteria, but not adequate. Iodine test will come back negative long before conversion to maltose is completed. It only tests for large starches. Once alpha has broken down into medium chains iodine test will be negative, but its still highly unfermentable.

A low beta dominant (below 147ish), or a low diastatic mash (mostly amber/brown malt) might take 90 minutes...but, a 150+, mostly pale malt mash is done well before the 60 minute mark, let alone 90.
If you look at the recipe, he's only trying to get down to 1.017 (from 1.068). So, there's not a lot of worry (in my mind at least) about making the wort as fermentable as possible.

As far as your second comment, well, the mash temp listed for the recipe is 148, so I don't know why you mentioned 150+.
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Old 10-24-2011, 03:37 AM   #9
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If you look at the recipe, he's only trying to get down to 1.017 (from 1.068). So, there's not a lot of worry (in my mind at least) about making the wort as fermentable as possible.

As far as your second comment, well, the mash temp listed for the recipe is 148, so I don't know why you mentioned 150+.
Fair enough. Yes, I should have read more closely.

At 148, iodine test should be negative at the 30 minute mark or before. And maltose conversion should be completed by 60. The concern would be with falling much below 148. If you're using a cooler MLT, then you might lose several degrees over the hour (I lose 5 degrees in 60 minutes). You'd be finishing at 143 and have an average of 145...if you mash-in at 148. THAT would take longer to ferment. So, I'd target my mash-in temp so that my loss in the MLT ended at 147 or so. Then 60 minutes should be plenty fine.

In the end 1.017 might be hard to stop at, when mashing at this low of a temp. I'd expect the mash to be more fementable than that at 148. I usually end at 1.012 (or below) when mashing for 60 minutes at that temp.
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Old 10-24-2011, 03:42 AM   #10
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Fair enough. Yes, I should have read more closely.

At 148, iodine test should be negative at the 30 minute mark or before. And maltose conversion should be completed by 60. The concern would be with falling much below 148. If you're using a cooler MLT, then you might lose several degrees over the hour (I lose 5 degrees in 60 minutes). You'd be finishing at 143 and have an average of 145...if you mash-in at 148. THAT would take longer to ferment. So, I'd target my mash-in temp so that my loss in the MLT ended at 147 or so. Then 60 minutes should be plenty fine.

In the end 1.017 might be hard to stop at, when mashing at this low of a temp. I'd expect the mash to be more fementable than that at 148. I usually end at 1.012 (or below) when mashing for 60 minutes at that temp.
I assume, in the second part of your post, that you're talking to the OP? It seems as though you're trying to convince/teach me, as if I were the OP.


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